The exhaust muffler of an internal combustion engine reduces exhaust noise of the engine by means of volume expansion of the exhaust gas and resonance attenuation in a plurality of chambers defined therein. Conventionally, in a small engine, a muffler is typically directly attached to the exhaust port of the engine by aligning an exhaust inlet of the muffler with the exhaust port of the engine, passing stud bolts provided to the engine through the holes provided in a flange extending radially around the exhaust inlet of the muffler and fastening nuts to the stud bolts.
Fastening such nuts is not necessarily easy because, usually, there is very little space between the engine and the muffler. To eliminate this problem concerning the accessibility to the fasteners for mounting the muffler, the use of stud bolts which are passed completely through the muffler itself was proposed in Japanese Utility Model laid Open Publication No. 62-200112 which was filed by the Assignee of the present application. In this mounting structure, a collar is fitted onto each of the stud bolts in order to control the extent of the collapsing of the muffler as the nuts are tightened. The need for such structural members capable withstanding compression force and relatively long stud bolts not only increases the weight of the muffler but also increases the manufacturing cost due to a large number of component parts required and the substantial labor involved in mounting it.
To overcome this problem, the Inventors have conceived to have the muffler made of two pieces so that the first, smaller piece may be attached to the engine and the second, larger piece may be attached to the first piece afterwards. It would be particularly convenient if the first piece consists of a tubular member serving as an inlet tube leading to the chambers defined in the muffler. In doing so, it is essential to eliminate any possibility of gas leakage from the interfaces between the first piece and the second piece and, yet, to simplify the process of assembling the second piece to the first piece. This is particularly significant because a plurality of chambers are typically defined inside the muffler for reducing exhaust noise and such an inlet tube has to pass through several wall members of the muffler defining these chambers, each time in an air tight manner.